1. Field of Invention
The invention pertains to an organic electroluminescence (OEL) display panel, and particularly to a full-color OEL display panel.
2. Background of the Related Art
An organic electroluminescence (OEL) device possesses the advantages of both a liquid crystal display (LCD) and an inorganic light-emitting diode (LED), such as compact size, high resolution, low power consumption, self-emission and fast response. Thus, an OEL device is considered to be a promising candidate for the next-generation of flat display panels.
Nowadays, full-color capability has gradually become a basic requirement for display panels. Furthermore, the quality demanded of full-color display panels has increased progressively. One important index for display panel quality is resolution that is defined by units of dpi (dot per inch). Generally, the pixel device of a display panel is composed of red (R), green (G) and blue (B) sub-pixel regions (hereinafter referred to as R, G and B sub-pixel regions) so as to provide full-color effects by mixing the light of these colors emitted from the individual sub-pixel regions of the pixel device. For current full-color LCD or OEL display panels, the sub-pixel regions therein are generally arranged in a stripe form, a mosaic form or a delta form.
The sub-pixel region arrangement based on the prior stripe form may be seen in FIG. 1A, in which each pixel device 100 in the matrix form is composed of R, G and B sub-pixel regions 110, 120, and 130 arranged row by row on a substrate. This arrangement is the simplest in terms of its manufacturing process, circuit design and driving method. However, the color mixing effect from the stripe-form display panel is the poorest. Refer to FIG. 1B for the prior sub-pixel region arrangement in a mosaic form, in which each two adjacent R, G and B sub-pixel regions 110, 120, and 130 are separated by the width of one sub-pixel region. Using this sub-pixel region arrangement, the color mixing effect from the corresponding display panel is improved. However, the circuit design and the driving method are complicated. Refer to FIG. 1C for the prior sub-pixel region arrangement in a delta form, in which each two adjacent R, G and B sub-pixel regions 110, 120, and 130 are separated by the width of 1.5 sub-pixel regions. Using this sub-pixel region arrangement, the color mixing effect from the corresponding display panel is further improved. However, the circuit design and the manufacturing process of the delta-form display panel are more complicated.
No matter which sub-pixel region arrangement is adopted in achieving full-color display capability, the manufacturing process of the sub-pixel regions determines the resolution of the full-color OEL display panel.
OEL devices generally are simply classified according to the EL materials used; the device using small molecules is called an organic light-emitting diode (OLED), the device using polymers is called a polymer light-emitting diode (PLED).
For a current full-color OLED device with RGB side-by-side format, a metal-mask alignment method is generally utilized to form the individual RGB sub-pixels. Therefore, the resolution of a OLED panel depends on the opening dimensions of the metal mask, which is related to the thickness of the metal mask and the ability of fine etching. Presently, the opening of a 30-micrometer(um)-thick metal mask is about 60 to 90 um. Therefore, a metal mask with 70 um opening can be utilized to make a full-color OLED panel with 121-dpi resolution. If a higher resolution of the OLED panel is required, a thinner metal mask or a finer etching skill has to be taken, which poses a considerable level of difficulty in the display panel manufacturing process.
For a full-color PLED panel, an ink-jet printing (IJP) method is often used, which is generally known as a precise and high-reproductive coating process. Hence, the IJP method could meet the requirements of automatic, miniaturized, low-cost, high-throughput and low-environment-impact manufacturing process. As for IJP, the higher the panel resolution is, the smaller the drop size is. However, in most situations, smaller ink drops pose a higher level of difficulty in the design of ink-jet head. Therefore, an important issue for the design of full-color OEL display panels is how to make an efficient arrangement of sub-pixel regions in the display panel.